<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
        body {
            margin: 0;
            min-width: 250px;
        }

        /* Include the padding and border in an element's total width and height */
        * {
            box-sizing: border-box;
        }

        /* Remove margins and padding from the list */
        ul {
            margin: 0;
            padding: 0;
        }

        /* Style the list items */
        ul li {
            cursor: pointer;
            position: relative;
            padding: 12px 8px 12px 40px;
            background: #eee;
            font-size: 18px;
            transition: 0.2s;

            /* make the list items unselectable */
            -webkit-user-select: none;
            -moz-user-select: none;
            -ms-user-select: none;
            user-select: none;
        }

        /* Set all odd list items to a different color (zebra-stripes) */
        ul li:nth-child(odd) {
            background: #f9f9f9;
        }

        /* Darker background-color on hover */
        ul li:hover {
            background: #ddd;
        }

        /* When clicked on, add a background color and strike out text */
        ul li.checked {
            background: #888;
            color: #fff;
            text-decoration: line-through;
        }

        /* Add a "checked" mark when clicked on */
        ul li.checked::before {
            content: '';
            position: absolute;
            border-color: #fff;
            border-style: solid;
            border-width: 0 2px 2px 0;
            top: 10px;
            left: 16px;
            transform: rotate(45deg);
            height: 15px;
            width: 7px;
        }

        /* Style the close button */
        .close {
            position: absolute;
            right: 0;
            top: 0;
            padding: 12px 16px 12px 16px;
        }

        .close:hover {
            background-color: #f44336;
            color: white;
        }

        /* Style the header */
        .header {
            background-color: #f44336;
            padding: 30px 40px;
            color: white;
            text-align: center;
        }

        /* Clear floats after the header */
        .header:after {
            content: "";
            display: table;
            clear: both;
        }

        /* Style the input */
        input {
            border: none;
            width: 75%;
            padding: 10px;
            float: left;
            font-size: 16px;
        }

        /* Style the "Add" button */
        .addBtn {
            padding: 10px;
            width: 25%;
            background: #d9d9d9;
            color: #555;
            float: left;
            text-align: center;
            font-size: 16px;
            cursor: pointer;
            transition: 0.3s;
        }

        .addBtn:hover {
            background-color: #bbb;
        }
    </style>
</head>

<body>

    <div id="myDIV" class="header">
        <h2 style="margin:5px">My To Do List</h2>
        <input type="text" id="myInput" placeholder="Title...">
        <span onclick="newElement()" class="addBtn">Add</span>
    </div>

    <ul id="myUL">
        <li>Hit the gym</li>
        <li class="checked">Pay bills</li>
        <li>Meet George</li>
        <li>Buy eggs</li>
        <li>Read a book</li>
        <li>Organize office</li>
    </ul>


</body>

</html>
<script>
    var myNodelist = document.getElementsByTagName("LI");
    var i;
    for (var i = 0; i < myNodelist.length; i++) {
        var span = document.createElement("SPAN");
        var txt = document.createTextNode("\u00D7");
        span.className = "close";
        span.appendChild(txt);
        myNodelist[i].appendChild(span);
    }




var close = document.getElementsByClassName("close");
var i;
for (i = 0; i < close.length; i++) {
  close[i].onclick = function() {
    var div = this.parentElement;
    div.style.display = "none";
  }
}

var list = document.querySelector('ul');
list.addEventListener('click', function(ev) {
  if (ev.target.tagName === 'LI') {
    ev.target.classList.toggle('checked');
  }
}, false);

function newElement() {
  var li = document.createElement("li");
  var inputValue = document.getElementById("myInput").value;
  var t = document.createTextNode(inputValue);
  li.appendChild(t);
  if (inputValue === '') {
    alert("You must write something!");
  } else {
    document.getElementById("myUL").appendChild(li);
  }
  document.getElementById("myInput").value = "";

  var span = document.createElement("SPAN");
  var txt = document.createTextNode("\u00D7");
  span.className = "close";
  span.appendChild(txt);
  li.appendChild(span);

  for (i = 0; i < close.length; i++) {
    close[i].onclick = function() {
      var div = this.parentElement;
      div.style.display = "none";
    }
  }
}
</script>